Two men, aged 56 and 53, and one women, 52, fleeing from the storm died while sheltering in a garden shed in Düsseldorf, when a poplar tree collapsed on the building on Monday evening.
Emergency services were able to rescue six others from building, two of whom were severely injured.
A 50-year old cyclist in Cologne and a second cyclist in Krefeld, North Rhine-Westphalia, also died when they were hit by falling trees. A sixth person, a 49-year-old man, collapsed and died as he was clearing up storm damage in Essen.
Heavy rain, lighting and hail also caused traffic delays on the railway, motorway and airports. Düsseldorf airport closed for an hour on Monday evening due to winds of up to 150 km/h.